Neurodevelopmental disabilities and mental health disorders are prevalent and have been steadily increasing in children worldwide over the last 2 decades. Common agricultural pesticides (i.e. organophosphates) have been associated with neurobehavioral alterations including attention deficit, impulsivity and cognitive decrease in children. However, there is currently no information of these associations among adolescents. Our preliminary work in Ecuadorian children suggests that neurobehavioral declines associated with pesticide exposures may improve over time after removal of the exposure. The most commonly used insecticides worldwide are neonicotinoids and cholinesterase inhibitors (i.e. organophosphates and carbamates). Neonicotinoids have not been studied in this context. Organophosphates may also influence thyroid hormone levels, another possible mechanism by which they could affect mental health. In 2008, we examined 313 children (ages 4-9 y) living in the agricultural county of Pedro Moncayo, Ecuador, as part of the Secondary Pesticide Exposure on Children and Adolescents (ESPINA) study. The objectives of this proposal are to: A) estimate the prevalence of pesticide exposures in blood (organophosphate, carbamate, neonicotinoid), and to assess the hypothesis that pesticides are associated with greater externalizing symptoms (i.e. hyperactivity, aggression, conduct problems), school problems (i.e. decreased attention and learning) and increased thyroid hormones among 80 adolescents (ages 12-17 y) of the ESPINA study in 2016. B) to expand the research capabilities of Pedro Moncayo County and Fundacin Cimas del Ecuador. We plan to strengthen the Local Community Information System (LCIS), a geocoded surveillance system of Pedro Moncayo County that includes socio-economic (SES), cultural and health information of over 15,000 residents, collected through community participation. We propose to conduct a Health Survey (interviews) of all household heads living in 1 of the 5 parishes of Pedro Moncayo County: Tupigachi (target n families=1000, nindividuals?5200, ?90% of the population). The survey will provide information on demographics, SES, occupation, geographic coordinates, access to social and health services (including mental health), economic activities, and morbidity of all household members. Impact: Few epidemiologic studies have assessed pesticide exposures in relation to mental health for extended periods of time and we know of no published studies on adolescents. Also, the LCIS is a powerful tool for needs assessments, intervention strategies and program evaluations, and has tremendous potential for rapid enrolment of participants in population-based studies. Community participation has made this an efficient and low-cost approach in the past; we are confident that the sample size and timeline will be met with the available resources. The findings of this study can guide the planning of larger investigations to assess determinants of mental health in agricultural settings.